Abstract This R13 proposal seeks support for a symposium and workshop at the Forsyth Institute October 11-12, 2018 on ?The Uncultivable Bacteria?. The overall objective of the Symposium is to increase understanding of the reasons 30 percent of the bacteria in the human oral cavity, and the majority of bacteria in the environment, remain ?uncultivable? using standard microbiological methods. The problem of ?uncultivability? is a major impediment to both host associated and environmental microbial research. The Candidate Phyla Radiation (CPR) is a recently recognized subdivision of bacteria representing 15% of bacterial diversity on earth. The CPR bacteria occur in essentially all environments, including the human oral cavity. To date, no members of the CPR have been cultured except for 10 isolates representing 5 species of human oral Saccharibacteria cultured by Forsyth investigators. The information to be presented at the symposium represents a paradigm shift in approach to culturing CPR and other as-yet-uncultivated groups of bacteria. This symposium and workshop will train a new cadre of investigators to tackle cultivation rather than attempt to rely solely on sequencing and in silico analysis. The conference will create a community of investigators who have previously resided in scientific silos that did not meet or communicate with each other: dental research, environmental microbiology, microbial ecology, and the life cycles and biology of obligate parasites. The Symposium will include poster presentations by attendees and talks by: Jill Banfield, Stephen Giovannoni, Kim Lewis, William Wade, Jeffrey Mclean, Floyd Dewhirst, Jessica Mark-Welch, Pallavi Murugkar, Xuesong He and Angela Douglas. The second day of the conference will be a workshop with live demonstration of the isolation and cultivation of human oral Saccharibacteria in coculture with appropriate host bacterial species. Detailed protocols will be distributed so that all attendees should be able to return to their laboratories and culture Saccharibacteria from their own mouths. Dissemination of approaches and protocols may enable widespread cultivation of taxa in the many phyla comprising the CPR. For environmental, industrial an d medical microbiology, this would be a transformative advance. For example, culturing CPR bacteria would greatly enhance our understanding of global carbon cycles and the development of biofuels by being able to utilize isolates of previously uncultured members of microbial dark matter. Knowledge presented in the symposium will enhance attendee?s approach to cultivating as-yet-uncultured members of the human oral cavity. Raising the percentage of cultivated organisms would allow a higher percentage of g enomes to be obtained for oral bacteria. The genome information provides the amino acid sequence of all genes. This increased information would greatly facilitate investigators mapping proteome and transcriptome data to species. This would significantly strengthen microbiome studies in dental research.